The present invention relates to a pneumatic tire and, more particularly, to a bias-ply tire suited for use as a front wheel tire on a motorcycle.
There is known a pneumatic tire which comprises a tire cover made of rubber material and having a tread portion, a pair of opposed side walls and a pair of opposed bead portions, and a reinforcing structure for preventing the tire from collapsing when it is at least partially deflated. The reinforcing structure includes a bias-ply carcass structure, embedded in the tire cover adjacent the inner surface thereof and having opposed ends turned up around and anchored to respective bead cores embedded in the bead portions, and at least one reinforcement layer made of cords of metallic material. The reinforcement layer in this known pneumatic tire is laid down on a bias relative to the midcircumferential plane of the tire and in opposite relation to the bias-ply carcass structure and has both ends terminating adjacent respective boundaries between the side walls and the bead portions and without being turned up around and anchored to the bead cores.
The known pneumatic tire of the above construction has been developed to provide such a feature that, even though puncture occurs in the tire during its use on a motorcycle, the motorcycle can be driven at a predetermined speed to the nearest possible repair shop without substantially adversely affecting the punctured tire. This known pneumatic tire is advantageous in that the tire during its use on a motorcycle is not readily crushed upon puncture thereof and the presence of the reinforcement layer allows the rigidity of the tire to be substantially retained to such an extent that the motorcycle having a payload imposed thereon can be driven at a reasonable speed to the nearest possible repair shop.
Although the known pneumatic tire of the above construction is satisfactory in that a motorcyclist need not be embarrassed at the time the tire on his motorcycle being operated has been pierced, some disadvantages have been found when it is used as a front wheel tire on the motorcycle. These disadvantages include reduction in cushioning effect of the tire with consequent reduction in riding comfort and reduction in steerability of the motorcycle and are attributable to the fact that, where the tire inflated to a normal pneumatic pressure is used as mounted on a front wheel of the motorcycle and where the tire inflated to a normal pneumatic pressure is used without a relatively excessive load imposed thereon, the tire in question tends to exhibit an excessive rigidity. These are particularly considerable where the motorcycle is driven at a speed of about 60 km/hr. or more.
Specifically, the reduction in cushioning effect of the tire due to the excessive rigidity thereof is undesirable not only because of the consequent reduction in riding comfort, but also because of a considerable amount of vibrations being transmitted to the prime mover, that is, the engine. In addition, the reduction is steerability tends to force the driver or motorcyclist to over-steer during high speed drive.